Improvement in furnace-grates



heat to which they are to be subjected.

CALVIN M. Nonrnnnr, or Nnvv YORK, N. Y.

IMPROVEMENT IN FURNACE-GRATES.

Specication forming part of Letters Patent No. 117,319, dated July 25,1871.

To all whom it may concern:

Be it known that I, CALvIN M. NORTHRUP, of the city and State of NewYork, have invented certain Improvements in the Uonstruc` tion of Gratesfor Furnaces of Steam-Boilers,- &c., of which the following is aspeciication:

My invention, briefly, consists in combining in a grate, for the usesabove mentioned, alternate straight and corrugated bars, andtie-bolting77 a series of such bars together, i'or advantages andreasons set forth hereinafter.

As I tie-bolt my grate-bars, necessarily, to accomplish my object in theconstruction of the grate, as presently to be descibed, I dispense withthe lugs or projections that are usually cast on the sides ofgrate-bars, and, in so far as relates to the bar itself, save metal anddo not impede the draught; and the tie-bolts and thimbles binding thebars in position will ontlast several sets oi' grate-bars, and can bcmany times used.

As above stated, I use in my compound grate an alternation of fiat-sidedbars and corrugated bars, and in different furnaces, according to size,length oi' bars wanted, and the intensity of the I may alternate thedifferent styles of bars in pairs or in relatively odd numbers.

rlhe flat-sided bar that I prefer to use is represented byv A, Figure l,on the accompanying drawing, that igure representing a cross-section (ofa section) of grate on `my plan, cutting through one of the tie-bolts,and the rings or thimbles b fitted loosely on the tie-bolts c c, andabutting against the bars between which they are interposed, to hold thebars apart at distances corresponding to the width and numberoi'thimbles so interposed, to suit the nature oi' fuel (size of coal,for instance) to be used on the given grate. Fig. 2 is a plan Viewcorresponding to Fig. 1. On Fig. 1 one of the flat-sided bars A and oneoi' the corrugated bars B are section-lined 5 also a couple or' thethimbles between them, b. For my use in my improved grate I extend theconcaves oi' the corrugated bar to the top edge ofthe bar, and similarlyextend the line of the convex of each corrugationstraight to the top ofthe bar, the bottom line being waved or corrugated its entire length.Thus in this corrugated bar there is no rib, strict- 1y termed, but thecorrugations blend into and constitute a characteristic of the bar as asimple whole. Fig. 3 is intended to represent a side view of acorrugated bar (broken in two) with the convolutions carried up to thetop, as stated, and cast with the holes below the iirefsurface toreceive the tie-bolts through the bar at corresponding distances fromeach end. In extra long bars I would put a tie-bolt, as (l G, Figs. land 2, through the middle of the set. I

The plain grate-bars in common use, having dat sides and taperingdownward on an acute angle when warped, or buckled upward when heated7do not shrink back to their normal level on cooling; but a grate-barcorrugated as described, when expanded by the heat yields, in a sense,as a spring 5 and being also the thinnest at the bottom portion where itis least exposed to the heat, this portion especially, I may say,springs back, drawing the upper surface of all the bars while cooling totheir original level. 0n the other hand, plain nat-sided bars of a givenlength and depth require less metal for a given vertical strength than abar with a corrugated lower portion 5 yet my corrugated bar is lighterand stronger than any other form of corrugated bar known to me, andsaves metal without sacricing strength to lightness.

For the above reasons I employ, alternate with the plain bar, as A, Fig.1, the corrugated bar, as described, (see B, same figure 5) and thecorrugated bars,bein g tie-bolted together with the plain bars incertain alternation, restrain the greater buckling tendency ofthelatter, and draw them back, while cooling, to their proper level, whilethe plain bars reduce the total cost of the grate and enhance itsgeneral strength.

By the use of the sectional thimbles b between the bars I can, by theadding or removal of one or more, correspondingly widen or decrease thedraught-space between them, as will be readily understood, and therebyfit the same grate for the use of different qualities of fuel 5 and thesaine size of pattern of bars can thus be used to cast any number ofbars with different openings, if oi' the same length, whereas now apattern is required for every set of bars to be of different openingsbetween.

I may add that the bars of my grate being tie-bolted together render itparticularly adapted for furnaces in which agitated or dumpinggrates arerequired.

The corrugated bar is less liable to warp when corrugated (transverselyof its length) nearly or quite to its top than when the flange alone iscorrugated. The tie-bolts and rings hold these bars firmly in position,and further tend to prevent their warping or springing laterally orVertically, and easily allow a bar to be added or removed froin the setor changed for another bar.

The bolts and thirnbles being entirely below the {ire-surface tend tokeep the tops of the bars cool, by allowing freer access of air ordraught, and freer access for raking than when lugs are carried up tothe fire-surface.

What I claim is- Witnesses:

WM. MONT STORM, FRANCIS G. BARTLETT.

